A vertical auger mixer typically consists of a stationary component which is generally an inverted, pyramid-shaped, oval truncated tub which has rotating augers inside used to mix animal feeds or other bulky loose material. This device using two or more vertically rotated, horizontally opposed mixing augers of a generally cone-shaped configuration, requires a somewhat half pyramid-shaped transfer protrusion attached to the tub sidewall to allow a satisfactory mixing action. This transfer protrusion is in most cases a symmetrical shape located at the center point of the sidewall of the tub perpendicular to the point where the mixing augers come nearest to contact. The transfer protrusion has a base which is concave and generally follows the contour of the vertical auger base. The transfer protrusion also has a tip which commonly terminates generally at the highest point of the auger flight. The transfer protrusions fill in the empty area or void where the augers do not contact the feed material. This void is known as a dead or inactive mixing area.
Fully or near symmetrical transfer protrusions used by most manufacturers do not provide efficient transfer of the mixed material from one auger to the next. A problem arises in that the product being mixed tends to remain (rotate) in the area of the auger where it is first located thus creating dead spots. This extends the mixing time required to fully mix the different feed ration ingredients throughout the entire batch.
It is a general object of the present invention to provide a vertical agricultural multi-auger mixer which optimizes mixing of agricultural materials by maximizing transfer of the mixed material from one auger to the next.
The invention is directed towards tub-mounted vertical mixing augers used in combination with transfer protrusions having a unique half pyramid shape, which improves the end-to-end mixing performance of a multiple vertical auger mixer. The transfer protrusion involved in this invention has a base, which is generally symmetrical in shape. The portion of the half pyramid-shaped protrusion where rotation of the vertical auger approaches rises from its base along the tub side to a tip near the top of the tub at a given angle. The side of the half pyramid-shaped protrusion which is away from the approach of the rotating vertical auger rises from the base at an angle which brings its tip to a point at a lower position on the tub sidewall. This allows material to advantageously roll or fall away from the action of the auger and the protrusion at a more rapid rate. This also allows the material to transfer to the adjacent auger more efficiently which improves the mixing action and speeds the emptying of the mixer. The key feature is to maintain or increase the pressure in the loaded output side of the auger against the protrusion, and to reduce or drop the pressure in the unloaded input side of the auger away from the protrusion while preventing dead (inactive) spots at the base of the protrusion next to the tub floor. The size and shape of the protrusion can be of a variety of shapes and sizes to accommodate different sizes and mixers while maintaining the advantages stated above.
In one aspect of the invention, a vertical agricultural mixer has a mixing tub defined by a pair of opposing end walls, first and second opposing sidewalls, a bottom wall and an open top. First and second vertical mixing augers are mounted in the mixing tub and are rotatably driven in the same direction therein for lifting and mixing agricultural materials together within the mixing tub. The invention is improved by first and second agricultural material-engaging transfer protrusions adjacently disposed along each opposed sidewall between the mixing augers and the mixing tub. The transfer protrusions have asymmetrical, upwardly tapering shapes with tips that are vertically spaced from each other and lie along a common vertical line on each side of the sidewalls to permit agricultural material to continuously and more efficiently transfer between the rotating mixing augers in order to improve mixing action in the tub.
During mixing, pressure is increased in a loaded output side of the first mixing auger against the one transfer protrusion closest thereto. Pressure is reduced in an unloaded input side of the second mixing auger away from the other transfer protrusion while preventing dead mixing spots on bottom ends of the transfer protrusions. A pressure gradient is created between the adjacently disposed first and second transfer protrusions that substantially minimizes flow of material from the first mixing auger over the second transfer protrusion on the second sidewall against a flow of material being transferred from the second mixing auger over the first transfer protrusion. The pressure gradient also substantially minimizes flow of material from the second mixing auger over the second transfer protrusion on the first sidewall against the flow of material being distributed from the first mixing auger over the first transfer protrusion.
In the preferred embodiment, a first transfer protrusion is located on the first sidewall and has a concave base following a contour of a lowest flight of the first mixing auger and rises to the tip at a given angle along a first guide surface. A second transfer protrusion on the first sidewall has a concave base following the contour of the lowest flight of the second mixing auger and rises to the tip along a second guide surface lying at a given angle which is different and less steep than the angle of the first guide surface on the first transfer protrusion. A third transfer protrusion on the second sidewall is similar to the first transfer protrusion and is located adjacent to the second mixing auger. A fourth transfer protrusion on the second sidewall is similar to the second transfer protrusion and is located adjacent to the first mixing auger. Each transfer protrusion preferably has a half pyramid shape. The common vertical line on each sidewall is coincident with a vertical plane transversely bisecting the mixing tub. The tips of the second and fourth transfer protrusions are positioned below the top ends of the vertical posts of the mixing augers.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.